This invention relates to novel metal silicate treated minerals which are receptive toward silane coupling agents. More particularly this invention relates to metal silicate treated inorganic mineral fillers, to a process for producing same, and to polymer composite compositions containing said treated fillers and silane coupling agents, as well as to silane modified metal silicate treated inorganic mineral fillers, and to polymer composite compositions containing said silane modified metal silicate treated inorganic mineral fillers.
The use of finely divided particulate and fibrous mineral materials, commonly referred to as mineral fillers or mineral pigments, for compounding into rubbers, resins, paints, inks, and other substances to form composite compositions is well known in the art. For instance, the use of nonsiliceous mineral fillers, e.g. natural and synthetic calcium carbonates, and partially siliceous synthetically coprecipitated mixed structural pigments, e.g. calcium carbonate-silica and calcium carbonate-metal silicate, as filler components in polymer-filler composites is well known as shown e.g. by British Pat. No. 838,903 and U.S. Pat. Nos. 2,928,802; 3,152,001 and 3,290,165. Moreover, certain wholly siliceous fillers, e.g. natural and synthetic silica fillers and metal silicate fillers, when used as filler components in polymer-filler composites are known to respond to the action of organosilane coupling agents with the production of improved cured composite properties as seen e.g. by U.S. Pat. Nos. 2,665,264; 2,744,879; 2,831,828; 2,831,829; and 2,897,173. However, natural and synthetic calcium carbonates and other non-siliceous mineral fillers do not show any significant or useful response in the presence of organosilane coupling agents by way of improved properties in the finished polymer composites. Since certain non-siliceous mineral fillers, particularly calcium carbonate, are among the most abundant, economical and widely used particulate fillers employed in polymer-filler composites, their lack of response to organosilane coupling agents has constituted a significant area of technological disadvantage in the development of improved polymer-filler composite compositions.
It has now been discovered that metal silicate treated inorganic mineral products can be prepared which can be employed along with organosilane coupling agents in polymer composites to confer improved properties in the finished composites and that said metal silicate treated mineral products can be further modified with organosilane coupling agents to form organosilane modified metal silicate treated mineral products which can also be employed as fillers in polymer composites to confer improved properties in the finished composites.